What's new in Java 12: How to use switch expressions instead of traditional switch statements

Java is a programming language widely used in software development. With the continuous development of technology, Java is constantly updated to add new features and improvements. Java 12 is a version released in 2019, which introduces an important new feature: switch expressions. This article will introduce this new feature and show how to use switch expressions to replace traditional switch statements.

In early versions of Java, we used the switch statement to implement multi-branch conditional control. For example, depending on the value of a variable, we can execute different blocks of code. However, the traditional switch statement has some limitations, such as only using constants as branch conditions and lack of flexibility and simplicity. New features in Java 12 solve these problems by introducing switch expressions.

First, let us look at an example of a traditional switch statement:

int dayOfWeek = 1;
String dayName;

switch(dayOfWeek) {
    case 1:
        dayName = "Monday";
        break;
    case 2:
        dayName = "Tuesday";
        break;
    case 3:
        dayName = "Wednesday";
        break;
    case 4:
        dayName = "Thursday";
        break;
    case 5:
        dayName = "Friday";
        break;
    default:
        dayName = "Invalid day";
        break;
}

System.out.println(dayName);

The above code assigns dayName according to the value of the variable dayOfWeek Name the corresponding day of the week and print it out. However, using a traditional switch statement can appear lengthy and cumbersome, especially if there are many branch conditions.

The switch expression in Java 12 is implemented through the -> symbol, making the code more concise. The following example shows how to use a switch expression to accomplish the same function as the traditional switch statement above:

int dayOfWeek = 1;
String dayName = switch(dayOfWeek) {
    case 1 -> "Monday";
    case 2 -> "Tuesday";
    case 3 -> "Wednesday";
    case 4 -> "Thursday";
    case 5 -> "Friday";
    default -> "Invalid day";
};

System.out.println(dayName);

By using a switch expression, we can put the branch condition and code block in one-> ; makes the code more concise and readable. This way of writing is very similar to the way of writing Lambda expressions, and is more in line with modern programming style.

In addition to using the switch expression for variable assignment, it can also be used for the return value of a method. For example, we can write a method to return the corresponding result based on the passed in parameters:

public static String getDayName(int dayOfWeek) {
    String dayName = switch (dayOfWeek) {
        case 1 -> "Monday";
        case 2 -> "Tuesday";
        case 3 -> "Wednesday";
        case 4 -> "Thursday";
        case 5 -> "Friday";
        default -> "Invalid day";
    };

    return dayName;
}

public static void main(String[] args) {
    int dayOfWeek = 3;
    String dayName = getDayName(dayOfWeek);
    System.out.println(dayName);
}

In the above code, we get the corresponding day of the week by calling the getDayName method and passing in a parameter Several names. A switch expression is used inside the method to complete this function and finally return the result.

To sum up, the switch expression introduced in Java 12 is a very useful new feature. It makes the code more concise and readable, and can replace the traditional switch statement. We can choose to use switch expressions according to specific circumstances to improve the readability and maintainability of the code.

(Note: The code examples in this article are based on Java 12 version and use new features. Please ensure that your development environment supports Java 12 or higher.)

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